Preparation method of sound insulation pad in automobile front wall and front wall metal plate with sound insulation pad

Abstract

The invention belongs to the technical field of automobile front wall sound insulation pads, and particularly relates to a preparation method of an automobile front wall inner sound insulation pad and a front wall metal plate with the sound insulation pad. Three-dimensional modeling data of an automobile and surrounding boundary conditions of a front wall assembly are obtained, and the thickness distribution interval of the sound insulation pad is determined; dividing areas, predicting sound reduction index according to sound source load, and adjusting thickness distribution after comparing with a target. And determining a multi-layer structure of the PU foaming layer, the re-coating layer, the EVA layer and the bi-component cotton layer according to the adjusted thickness. Heating a recoating material, placing the recoating material in a lower die, injecting a PU foaming AB material into an upper die for foaming and bonding, and punching after die pressing to obtain a body. The body is fixed to a front wall metal plate through an elastic piece buckle and a projection welding stud, and an EPP footstep cushion block is installed on the copilot side. Sound insulation and heat insulation are realized through thickness optimization of a composite material layer structure and simulation driving; continuous production is achieved through the mold integrating plastic uptake, foaming and punching, and efficiency is improved. The sound insulation pad is effectively prevented from shifting through the fixing mode that the elastic piece buckles are matched with the projection welding studs.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of automobile front wall sound insulation pad, and particularly relates to a preparation method of an automobile front wall inner sound insulation pad and a front wall sheet metal with the sound insulation pad. BACKGROUND

[0002] The front wall sound insulation pad is a very important part of the interior of a whole vehicle, is used for covering the visible area of the automobile front wall sheet metal part, the side door sill sheet metal part and the like which is not covered, beautifies the vehicle interior environment, and is also an important acoustic treatment part which can block road noise in vehicle driving and provide a comfortable vehicle riding environment for passengers.

[0003] The front wall inner sound insulation pad in the related art is designed in a uniform thickness distribution mode, and the sound insulation effect is poor due to insufficient thickness in the areas such as the front of the engine and the vicinity of the air conditioning hot water pipe, although the noise load is strong. The noise load is weak in the edge transition area, and the material is wasted due to excessive thickness, which cannot meet the sound insulation requirements of the vehicle NVH performance decomposition, additionally increases the weight of the vehicle body, and it is difficult to balance the acoustic performance.

[0004] In the related art, the sound insulation layer such as double-component cotton is arranged towards the front wall sheet metal side, and the PU foaming sound absorption layer is arranged towards the cockpit side, so that the noise attenuation path is reversed, and the sound insulation effect is weakened. The interlayer combination is realized by using a normal temperature adhesive, the adhesive is easily softened and fails in the high temperature environment of die pressing, and after long-term use, gaps appear between the layers, and the sound insulation performance gradually attenuates. SUMMARY

[0005] The application provides a preparation method of an automobile front wall inner sound insulation pad, which realizes lightweight, sound insulation, heat insulation and corrosion resistance improvement. The thickness distribution balance performance and weight are simulated and optimized, and the production efficiency is improved by integrating the suction foaming and punching die.

[0006] The method comprises the following steps: S101: acquiring three-dimensional modeling data of a vehicle and peripheral boundary conditions of front wall assembly arrangement, and determining a thickness distribution interval of the front wall inner sound insulation pad; S102: dividing a plurality of regions of the front wall inner sound insulation pad in the thickness distribution interval, and predicting sound insulation amounts of the regions according to sound source load distribution data; S103: comparing the predicted sound insulation amounts of the regions with preset target sound insulation amounts, and adjusting the thickness distribution of the front wall inner sound insulation pad according to a comparison result; S104: determining, according to the adjusted thickness distribution, a multilayer composite material structure of the front wall inner sound insulation pad which comprises a PU foaming layer, a recoating layer and a sound insulation layer comprising an EVA layer and a double-component cotton layer; S105: heating and softening the recoating layer material corresponding to the recoating layer, and placing the recoating layer material in a lower die of a suction foaming and punching die; S106: Inject the prepared PU foaming AB material into the upper die of the blister foaming and punching die, so that the PU foaming AB material is foamed and bonded on the re-coating layer; S107: After molding, cutting is performed by a punching cutter integrated on the blister foaming and punching die, to obtain a molded front wall inner sound insulation pad; S108: The front wall inner sound insulation pad is fixed on the front wall sheet metal by a spring buckle and a projection welding stud, and an EPP foot pad block is installed on the side of the co-pilot.

[0007] Preferably, S101 specifically includes the following steps: The CATIA format three-dimensional modeling data corresponding to the target commercial vehicle front wall assembly is called, and a point site mapping tool is used to collect the installation parameters of the butt joint parts on the front wall sheet metal, including wire harness mounting points, brake pedal mounting points, throttle pedal mounting points, and air conditioning hot water pipe mounting points; The collected installation parameters of each butt joint part are converted into an occupying range in the three-dimensional modeling space, and a minimum gap threshold value between the front wall inner sound insulation pad and each butt joint part is set; Combined with the space profile of the three-dimensional modeling data and the minimum gap threshold value, a plurality of regions of the front wall inner sound insulation pad are divided and an initial thickness of each region is allocated, and by calculating the average thickness of each region, the upper and lower limits of the thickness distribution range of the front wall inner sound insulation pad are determined.

[0008] Preferably, S102 specifically includes the following steps: A light commercial vehicle front wall sound source test bench is built, four operating conditions of idling, uniform speed, 5th gear full throttle, and 6th gear full throttle are selected, sound pressure level data of the corresponding regions of the front wall assembly under each operating condition are collected, and the sound pressure level data are converted into sound source load values at each position; The sound source load values collected under each operating condition are matched to the corresponding regions one by one according to the spatial projection range of the regions of the front wall inner sound insulation pad divided in S101, to obtain a sound source load distribution set for each region. Based on the statistical energy simulation analysis method, an acoustic subsystem model corresponding to each region of the front wall inner sound insulation pad is established, material parameters of each region are substituted, and the sound insulation amount of each region is calculated in combination with the average thickness formula of the material layer thickness.

[0009] Preferably, S103 specifically includes the following steps: The target sound insulation amount of the front wall assembly obtained based on the decomposition of the overall vehicle NVH performance is called, the target sound insulation amount of each region is matched to the corresponding region one by one according to the regions divided in S102, and a judgment threshold value for comparing the sound insulation amount is set; The average thickness of each region after the initial thickness allocation is analyzed, and each region is compared with the average thickness, and the region with a thickness greater than or equal to the average thickness is defined as a thick region, and the region with a thickness less than the average thickness is defined as a thin region. The predicted sound insulation amount of each region is compared with the target sound insulation amount and the determination threshold value of the corresponding region respectively; if the predicted sound insulation amount is less than (the target sound insulation amount minus the determination threshold value), the thickness of the corresponding thin area is increased or the area ratio thereof is reduced; if the predicted sound insulation amount is greater than (the target sound insulation amount plus the determination threshold value), the thickness of the corresponding thick area is reduced or the area ratio thereof is reduced.

[0010] Preferably, S104 specifically comprises the following steps: The adjusted total thickness of each region is extracted S103, and the total thickness of each region is decomposed into the thickness of the PU foaming layer, the thickness of the heavy coating layer, the thickness of the EVA layer and the thickness of the double-component cotton layer, forming a layered thickness distribution table of each region; According to the assembly direction and the acoustic propagation path of the front wall inner sound insulation pad, the layering order of the multi-layer composite material is determined as: heavy coating layer, PU foaming layer, EVA layer, double-component cotton layer, wherein the double-component cotton layer faces the cockpit side, and the heavy coating layer faces the front wall panel side; The specification parameters of each layer of material are determined, and the interlayer bonding mode is determined.

[0011] Preferably, S105 specifically comprises the following steps: The heavy coating layer material is cut to adapt to the lower die cavity of the vacuum foaming punching die, and the lower die of the punching die is cleaned and defect pretreated; The cut heavy coating layer material is placed in an oven and heated to a softened state; The opening and closing state of the vacuum foaming punching die is adjusted, the heated and softened heavy coating layer material is positioned and placed in the lower die after spraying the release agent in the lower die cavity of the punching die.

[0012] Preferably, S106 specifically comprises the following steps: The mass ratio of A material and B material is calculated according to the PU foaming density specification 60kg / m³, the corresponding mass of A material and B material is weighed by an electronic scale, and the double-shaft mixer is placed; The mixed PU foaming AB material is loaded into a perfusion gun with a pressure sensor, and is injected through the injection port of the upper die of the mold at a constant pressure, so that the AB material uniformly fills the upper die cavity and contacts the surface of the lower heavy coating layer; The mold heating system is started, the temperature of the upper die is increased to the preset temperature and kept constant, the foaming reaction of the AB material is triggered, and the upper and lower molds are kept at the preset gap during the foaming process, so that the PU layer after foaming and the heavy coating layer realize chemical adhesion through intermolecular force.

[0013] Preferably, S107 specifically comprises the following steps: After the mold pressing curing is completed, the curing state of the material in the mold is detected; The down pressure and cutting speed parameters of the punching cutter die are set, the positioning pin of the mold cavity is taken as the reference, and the punching driving mechanism is started to drive the cutter die to move downward; After the cutting is completed, the mold is opened, the cut composite structure part is taken out, the edge waste is separated, and the formed front wall inner sound insulation pad is obtained.

[0014] Preferably, S108 specifically comprises the following steps: In the direction of the re-coating layer facing the engine compartment, the front wall inner sound insulation pad is preliminarily aligned with the plurality of projection welding studs on the front wall sheet metal assembly, the mounting holes punched out of the front wall inner sound insulation pad are sequentially passed through the corresponding projection welding studs, positioning and suspension are realized; A pressing force is applied to the front wall inner sound insulation pad suspended on the projection welding studs towards the sheet metal surface, the metal spring buckles in the remaining mounting holes are elastically deformed until the locking structure of the buckle passes over the thread root of the projection welding stud and is tightly clamped after springback, the fixing between the body and the sheet metal is completed. In the front wall area of the co-pilot, the foot pad block made of independent EPP material is molded into the clamping groove on the corresponding position of the front wall inner sound insulation pad in the direction of the bottom surface of the preset clamping structure, pressure is applied to embed and lock it, and the assembly of the pad block is completed.

[0015] According to another embodiment of the present application, a front wall sheet metal with a sound insulation pad is provided, comprising: a front wall inner sound insulation pad; The front wall inner sound insulation pad is fixed on the front wall sheet metal through projection welding studs and buckles; An EPP foot pad block is installed on the co-pilot side of the front wall sheet metal; The front wall inner sound insulation pad is provided with a sound insulation layer, a re-coating layer and a PU foaming layer.

[0016] From the above technical solutions, the present application has the following advantages: The automobile front wall inner sound insulation pad preparation method provided by the present application collects CATIA three-dimensional modeling data, collects docking part installation parameters and converts them into a space occupation range, and divides the thickness distribution interval. A multi-working-condition test bench is built to collect sound source load data, and the load set is matched and statistically simulated to predict the sound insulation amount. By comparing the predicted sound insulation amount with the target value, the thickness and area ratio of the thick / thin area are adjusted. The thickness of each area is matched, the sound insulation performance of the strong noise area in front of the engine meets the standard, and the material redundancy in the edge area is eliminated, thereby balancing the weight and acoustic performance while ensuring the NVH performance.

[0017] The present application determines the laminated structure in the order of re-coating layer, PU foaming layer, EVA layer and double-component cotton layer, and matches the noise propagation path. The PU foaming layer is fused and bonded with the re-coating layer and the EVA layer by using mold pressing at high temperature, and the EVA layer is pre-fixed by needle punching with the double-component cotton layer. Noise is gradually attenuated in the multi-layer structure, and the progressive barrier improves the sound insulation efficiency. The interlayer bonding strength adapts to the mold pressing process and long-term use requirements, and ensures the stability of the sound insulation performance.

[0018] The present application covers four typical working conditions of idle, uniform speed, 5th gear full throttle and 6th gear full throttle, and sound source load data is collected through an array type sound pressure sensor. In simulation, the front wall sheet metal and air layer are set as a correlated subsystem, and the sound insulation amount is calculated by substituting the boundary conditions and material parameters of the connecting piece, so that the sound insulation amount prediction is improved, and the designed sound insulation pad can meet the NVH performance requirements under all working conditions. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the present application, the drawings required to be used in the description will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0020] Figure 1 It is a schematic diagram of the front wall sheet metal; Figure 2 It is a schematic diagram of the front wall sheet metal embodiment; Figure 3 It is a schematic diagram of the front wall inner sound insulation pad; Figure 4 It is a flow chart of the preparation method of the front wall inner sound insulation pad of the automobile. DETAILED DESCRIPTION

[0021] As shown in the drawings, Figures 1 to 3 The front wall sheet metal with the sound insulation pad includes: the front wall inner sound insulation pad 6 prepared by the preparation method; the front wall inner sound insulation pad 6 is fixed on the front wall sheet metal 4 through the projection welding stud 5 and the buckle 7; the EPP foot pad 8 is installed on the co-driver side of the front wall sheet metal 4; the front wall inner sound insulation pad 6 is provided with a sound insulation layer 1, a re-coating layer 2 and a PU foaming layer 3.

[0022] A plurality of round holes are opened on the front wall inner sound insulation pad of the present application, the corresponding positions of the vent cover plate sheet metal are provided with projection welding studs, and the round holes are fixed through the elastic sheet buckle by penetrating the projection welding studs.

[0023] Optionally, 11 round holes are opened on the front wall inner sound insulation pad. The holes on the two sides of the front wall inner side are used for fixing the A-pillar lower trim panel and the carpet, and are fixed by using nuts. In order to improve the crash performance, the EPP foot pad is increased on the co-driver side of the front wall inner side to prevent the carpet from moving in a severe collision, which will cause secondary injury to the occupant. In order to effectively protect the personnel and reduce the impact of the collision, the best protection under different collision intensities is provided.

[0024] Optionally, the specification of the PU foaming of the present application is 60kg / m³, the specification of the EVA is 2300g / ㎡, and the specification of the double-component cotton is 600g / ㎡. The front wall inner sound insulation pad and the wire harness use the projection welding studs of the front wall sheet metal, and are installed on the outside of the front wall inner sound insulation pad by using the buckle strap.

[0025] The method for manufacturing the automobile front wall inner sound insulation pad will be described in detail below. For the purpose of illustration but not for the purpose of limitation, specific details such as specific system structures, techniques, and the like are presented in order to provide a thorough understanding of the embodiments of the present application. However, it should be apparent to those skilled in the art that the present application can be implemented in other embodiments without the specific details.

[0026] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts fall within the scope of protection of the present application.

[0027] Please refer to Figure 4 Fig. 1 shows a flow chart of the method for manufacturing the automobile front wall inner sound insulation pad in an embodiment, and the method comprises the following steps: S101: Obtain the three-dimensional modeling data of the vehicle and the peripheral boundary conditions of the front wall assembly arrangement, and determine the thickness distribution interval of the front wall inner sound insulation pad.

[0028] In some embodiments, the basic size framework of the front wall assembly is obtained by calling the CATIA three-dimensional modeling data, the installation parameters of the butt joint are collected, the parameters are converted into a space occupation range and a gap threshold is set, and the arrangeable space boundary of the sound insulation pad is determined. By preliminarily dividing the region, distributing the initial thickness and calculating the average value of the thickness, the thickness interval is determined in combination with the space limitation, so that the thickness distribution is always within the constraint range of the actual assembly space.

[0029] S101 specifically comprises the following steps: S1011: Call the CATIA format three-dimensional modeling data corresponding to the target commercial vehicle front wall assembly, use a point mapping tool to collect the installation parameters of the butt joint on the front wall sheet metal, and the butt joint includes a wire harness installation point, a brake pedal installation point, an accelerator pedal installation point, and an air conditioning hot water pipe installation point.

[0030] In some embodiments, the CATIA three-dimensional model data corresponding to the commercial vehicle front wall assembly is called from the database, and the CATIA three-dimensional model data includes the curved surface profile of the front wall sheet metal, the three-dimensional coordinate and other size information of each installation hole.

[0031] Using the point mapping tool, the installation parameters of each interface part on the front wall panel are obtained, including the center distance of the wire harness mounting point fixing hole, the protruding height of the brake pedal mounting point relative to the front wall panel reference surface, the horizontal offset of the accelerator pedal mounting point, the pipe diameter of the air conditioning hot water pipe mounting point, and the extension direction. These parameters are associated and matched with the corresponding positions in the CATIA three-dimensional model file to ensure that the parameters and model positions correspond one by one.

[0032] S1012: Convert the collected installation parameters of each interface part into a placeholder range in the three-dimensional modeling space, and set the minimum gap threshold between the front wall inner sound insulation pad and each interface part.

[0033] In some embodiments, the installation parameters of each interface part are converted into a placeholder area in the space coordinate system of the reference surface based on the outer surface of the front wall panel in the CATIA three-dimensional modeling data.

[0034] For example, the protruding height of the brake pedal mounting point is converted into a spatial placeholder height range above the reference surface, and the pipe diameter of the air conditioning hot water pipe mounting point is converted into a spatial placeholder radial range to the side of the reference surface. Then, according to the assembly requirements of the front wall inner sound insulation pad, a corresponding minimum gap threshold is set for each interface part, which covers the installation tolerance of the interface part and the vibration allowance of the interface part during vehicle operation.

[0035] S1013: Based on the space profile of the three-dimensional modeling data and the minimum gap threshold, divide the multiple regions of the front wall inner sound insulation pad and assign an initial thickness to each region. By calculating the average thickness of each region, the upper and lower limits of the thickness distribution interval of the front wall inner sound insulation pad are determined.

[0036] In some embodiments, the front wall assembly space profile presented by the CATIA three-dimensional modeling data is used as a boundary, and the spatial placeholder range of each interface part and the set minimum gap threshold are combined to preliminarily divide the front wall inner sound insulation pad into multiple independent regions, and assign an initial thickness value hi to each region. The average thickness hv of these regions is calculated by hv = ∑hi / n, where hi is the initial thickness of each region and n is the total number of divided regions. The maximum thickness allowed by the overall layout of the front wall assembly and the minimum thickness corresponding to the minimum gap threshold are combined to determine the upper and lower limits of the thickness of each region, which together constitute the thickness distribution interval of the front wall inner sound insulation pad.

[0037] In this embodiment, the upper and lower limits of the thickness interval are determined by calculating the average thickness and combining the spatial restrictions, so that the thickness distribution is within a reasonable spatial constraint.

[0038] S102: Within the thickness distribution interval, divide the multiple regions of the front wall inner sound insulation pad, and predict the sound insulation amount of each region according to the sound source load distribution data.

[0039] In some embodiments, the typical working conditions of the actual operation of the vehicle are simulated by the test bench, the sound pressure signals at different positions are collected by the array sensor, the sound pressure signals are converted into load values of energy quantized sound source intensity, and the actual sound source environment of the front wall area is restored.

[0040] The spatial coverage of the region is matched according to the matching, the discrete sound source load data is corresponded to the preset sound insulation pad region, and is integrated into the exclusive load set of each region.

[0041] The complex front wall acoustic system is divided into independent subsystems by using the statistical energy method, the material parameters and the thickness average value are combined, and the acoustic insulation capacity of each subsystem is calculated by the simulation tool.

[0042] S102 specifically includes the following steps: S1021: A light commercial vehicle front wall sound source test bench is built, four working conditions of idling, uniform speed, 5th gear full throttle and 6th gear full throttle are selected, sound pressure level data of the corresponding region of the front wall assembly under each working condition is collected, and the sound pressure level data is converted into sound source load values at each position.

[0043] S1022: The sound source load values collected under each working condition are matched to the corresponding region according to the spatial projection range of the front wall inner sound insulation pad region divided in S101, and the sound source load distribution set of each region is obtained.

[0044] In some embodiments, the three-dimensional spatial projection coordinates of each region of the front wall inner sound insulation pad divided in S101 are called, the geometric center of each region is taken as the reference, the rectangular coverage range of the region on the plane is demarcated, the installation coordinates of each sound pressure sensor in S1021 are compared with the rectangular coverage range of each region. If the sensor coordinates are within the coverage range of a region, the sound source load value corresponding to the sensor is included in the load set of the region; after matching all sensor data, the sound source load distribution set of each region under the idling, uniform speed, 5th gear full throttle and 6th gear full throttle working conditions is obtained.

[0045] In this way, the spatial coverage of the region is matched according to the matching, the discrete sound source load data is corresponded to the preset sound insulation pad region, and the discrete sound source data is integrated into the exclusive load set of each region.

[0046] S1023: Based on the statistical energy simulation analysis method, the acoustic subsystem model corresponding to each region of the front wall inner sound insulation pad is established, the material parameters of each region are substituted, the average value of the thickness of the region material layer is combined, and the sound insulation quantity of each region is calculated.

[0047] In some embodiments, the material parameters include the area density, thickness of the PU foam, EVA, and double-component cotton. According to the subsystem division rules of the statistical energy simulation analysis method, each region of the front wall inner sound insulation pad is defined as an independent acoustic subsystem, and the air layer between the front wall panel and the engine compartment and the cabin is taken as a related subsystem. Then, the physical parameters of the PU foam (density 60 kg / m3), EVA (area density 2300 g / m2), and double-component cotton (area density 600 g / m2) in each region, and the thickness of each material layer allocated in S101 are called to calculate the average thickness of the material layer of each region. Finally, the subsystem model, material physical parameters, and material layer average thickness are substituted into the statistical energy simulation analysis tool, and after running the simulation calculation, the sound insulation quantity values of each region under different working conditions are output.

[0048] In this way, the complex front wall acoustic system is divided into independent subsystems by using the statistical energy method, the physical parameters and thickness average of the materials are combined, and the acoustic blocking ability of each subsystem is calculated by the simulation tool.

[0049] S103: Comparing the predicted sound insulation quantity of each region with the preset target sound insulation quantity, and adjusting the thickness distribution of the front wall inner sound insulation pad according to the comparison result.

[0050] In some embodiments, the accurate regional target sound insulation quantity is obtained by vehicle NVH performance decomposition, a reasonable judgment threshold is set, and a clear and quantifiable benchmark is provided for sound insulation quantity comparison. Based on the statistical average of the current thickness of each region, the thick and thin regions are divided, and the region type that needs to be adjusted in thickness is located. By comparing the sound insulation quantity with the target value and the judgment threshold, the performance deficiency and redundancy are distinguished, the directional thickness or area adjustment is implemented for different region types corresponding to different states, and the adjustment action and performance demand are accurately matched.

[0051] S103 specifically includes the following steps: S1031: Calling the front wall assembly target sound insulation quantity obtained based on the vehicle NVH performance decomposition, matching the corresponding regional target sound insulation quantity one by one according to the region division in S102, and setting the judgment threshold for sound insulation quantity comparison.

[0052] In some embodiments, the target sound insulation quantity of the commercial vehicle front wall assembly is called from the vehicle NVH performance design database, and the target sound insulation quantity is the front wall acoustic index obtained by reverse decomposition based on the cabin noise limit value during vehicle driving.

[0053] According to the acoustic contribution degree of each region of the front wall inner sound insulation pad divided in S102, the total target sound insulation quantity is proportionally decomposed into the regional target sound insulation quantity of each region.

[0054] Exemplarily, the region corresponding to the front of the engine is assigned a higher target sound insulation amount, and the edge transition region is assigned a lower target sound insulation amount. In combination with the error range of the acoustic test, a determination threshold is set to distinguish between three states of sound insulation amount, insufficient sound insulation amount, and redundant sound insulation amount.

[0055] S1032: Analyze the average thickness of each region after the initial thickness distribution in S101, and compare the current thickness of each region with the average thickness to define the regions with thickness greater than or equal to the average thickness as thick regions, and the regions with thickness less than the average thickness as thin regions.

[0056] S1033: Compare the predicted sound insulation amount of each region with the target sound insulation amount of the corresponding region and the determination threshold, respectively; if the predicted sound insulation amount is less than (target sound insulation amount - determination threshold), increase the thickness or reduce the area proportion of the corresponding thin region; If the predicted sound insulation amount is greater than (target sound insulation amount + determination threshold), reduce the thickness or area proportion of the corresponding thick region.

[0057] In some embodiments, the predicted sound insulation amount of each region obtained in S102 is compared with the target sound insulation amount of the region matched in S1031 and the determination threshold in both directions.

[0058] If the predicted sound insulation amount of a region is lower than the target sound insulation amount, it is determined that the sound insulation amount is insufficient, and the corresponding thin region is preferentially selected for adjustment: the thickness of the thin region is increased, and the adjusted thickness does not exceed the upper limit of the thickness distribution interval determined in S101.

[0059] If the thickness is still not sufficient after increasing, the area proportion of the thin region is further reduced. If the predicted sound insulation amount of a region is higher than the target sound insulation amount, it is determined that the sound insulation amount is redundant, and the corresponding thick region is selected for adjustment: the thickness of the thick region is preferentially reduced, and the adjusted thickness is not lower than the lower limit of the thickness distribution interval determined in S101.

[0060] If the thickness is reduced to the lower limit and there is still redundancy, the area proportion of the thick region is further reduced to avoid excessive adjustment affecting the overall coverage of the sound insulation pad.

[0061] In this way, the thickness distribution is finely adjusted, the adjustment amplitude and proportion are controlled to ensure that the sound insulation amount of each region meets the standard, and the structural stability of the sound insulation pad is ensured.

[0062] S104: According to the adjusted thickness distribution, the front wall inner sound insulation pad is determined to be composed of a multi-layer composite material structure of a PU foaming layer, a heavy coating layer, and a sound insulation layer containing an EVA layer and a double-component cotton layer.

[0063] In some embodiments, based on the sound insulation, sound absorption, and vibration reduction setting of each layer of material, the adjusted total thickness is accurately disassembled to each layer, so that the layered thickness matches the regional acoustic demand and total thickness limit. Combined with the path characteristics of noise propagation and the orientation requirements of the assembly space, the noise is gradually attenuated in the multi-layer structure, ensuring accurate adaptation of each layer and the assembly surface.

[0064] S104 specifically includes the following steps: S1041: Extract the adjusted total thickness of each region, disassemble the total thickness of each region into PU foam layer thickness, heavy coating layer thickness, EVA layer thickness, and double-component cotton layer thickness, and form a layered thickness distribution table for each region.

[0065] In some embodiments, for each region, the total thickness is disassembled according to the preset function, and the thickness ratio of the sound insulation layer is preferentially guaranteed to be not less than 40% of the total thickness, wherein the double-component cotton layer thickness is not less than 1.2 times the EVA layer thickness; the PU foam layer thickness is allocated according to the acoustic sound absorption demand, and the thickness ratio is controlled to be 30%-45% of the total thickness; the remaining thickness is allocated to the heavy coating layer, and the minimum thickness of the heavy coating layer is not less than 1.5 mm to ensure the vibration reduction performance.

[0066] In this embodiment, the adjusted thick region in S103 is disassembled according to the above-mentioned proportion. For the thin region, the PU foam layer thickness ratio is preferentially compressed to ensure that the sound insulation layer thickness meets the basic sound insulation demand, and finally a layered thickness distribution table covering all regions is formed, marking the specific thickness values of each layer in each region.

[0067] S1042: According to the assembly direction and acoustic propagation path of the front wall inner sound insulation pad, the layering order of the multi-layer composite material is determined as: heavy coating layer, PU foam layer, EVA layer, double-component cotton layer, wherein the double-component cotton layer faces the cockpit side, and the heavy coating layer faces the front wall sheet metal side.

[0068] In some embodiments, the noise propagation path of the front wall region is analyzed, and the noise propagates from the engine compartment to the cockpit through the front wall sheet metal and is gradually attenuated by the multi-layer structure of the sound insulation pad.

[0069] Optionally, combined with the assembly demand, the heavy coating layer needs to be directly attached to the front wall sheet metal to play a vibration reduction role, and can be set to face the sheet metal side.

[0070] The PU foam layer has excellent sound absorption performance and is arranged close to the heavy coating layer, which can further absorb the noise attenuated by the heavy coating layer.

[0071] The EVA layer has damping properties, connects the PU foaming layer and the double-component cotton layer, and forms a progressive acoustic barrier for sound absorption, damping, and sound insulation. The double-component cotton layer is soft and has excellent sound insulation performance, and is set towards the cockpit side to reduce the final transmission of noise to the cockpit. In combination with the U-shaped cross-sectional structure of the front wall inner sound insulation pad, the layer stacking order is confirmed to be consistent in the entire U-shaped area.

[0072] S1043: solidify the specification parameters of each layer material, and determine the interlayer bonding mode; The specification of the PU foaming layer is 60 kg / m³, the specification of the EVA layer is 2300 g / ㎡, the specification of the double-component cotton layer is 600 g / ㎡, the re-coating layer material is a blend of EPDM and EVA, and the interlayer adopts a hot melting bonding mode to adapt to the subsequent mold forming process.

[0073] In some embodiments, the specification parameters of each layer material are retrieved from the database and solidified to ensure matching with the initial scheme.

[0074] The PU foaming layer adopts a hard foaming material with a density of 60 kg / m³, the EVA layer adopts a high-damping EVA roll material with a surface density of 2300 g / ㎡, the double-component cotton layer adopts a needle-punched composite cotton with a surface density of 600 g / ㎡, and the re-coating layer adopts a blended material of EPDM and EVA in a mass ratio of 7:3.

[0075] This embodiment determines that the interlayer bonding mode is hot melting bonding: the PU foaming layer and the re-coating layer are melt-bonded through high temperature during mold pressing, the PU foaming layer and the EVA layer are attached through the heat-softening property of EVA, and the EVA layer and the double-component cotton layer are pre-fixed through a needle-punching process, to ensure that the multi-layer structure does not separate during mold pressing, and to form a continuous overall structure, ensuring the stability of the functions of each layer.

[0076] S105: heat and soften the re-coating layer material corresponding to the re-coating layer, and place it in the lower mold of the suction foaming and punching mold.

[0077] In some embodiments, the re-coating layer material is cut to adapt to the lower mold cavity, and the mold is pretreated to remove impurities and surface defects, to provide a form-matched material and a flawless mold base for the process.

[0078] This embodiment can use a high temperature of 230°C to melt and soften the EVA component in the re-coating layer material, maintain the structural support of the EPDM component, and make the overall material flexible enough to attach to the mold cavity. The mold operating space is also expanded through the air bag floating and rotating actions, the release agent forms an isolation layer between the mold cavity and the material, and the positioning pin limits the placement position of the material, to ensure the precise attachment of the material and the mold cavity.

[0079] S105 specifically includes the following steps: S1051: Trim the lower mold cavity of the re-coating material fitting blister foaming die, and clean and defect pretreat the lower mold of the die; S1052: Heat the trimmed re-coating material in an oven to a softened state; S1053: Adjust the opening and closing state of the blister foaming die, spray the lower mold cavity of the die with a release agent, and then position the heated and softened re-coating material in the lower mold.

[0080] As can be seen, the high temperature of 230°C melts and softens the EVA component in the re-coating material, maintains the structural support of the EPDM component, and makes the material as a whole flexible to fit the mold cavity. The mold operating space is expanded by the air bag floating and rotating action, the release agent forms an isolation layer between the mold cavity and the material, and the positioning pin limits the placement position of the material, ensuring accurate fitting of the material and the mold cavity.

[0081] S106: Inject the matched PU foaming AB material into the upper mold of the blister foaming die, and make the PU foaming AB material foam and bond on the re-coating layer.

[0082] S106 specifically includes the following steps: S1061: Calculate the mass ratio of A material and B material according to the PU foaming density specification 60 kg / m³, use an electronic scale to weigh the corresponding mass of A material and B material, and mix them in a double-shaft mixer to ensure uniformity and no air bubbles.

[0083] S1062: Load the mixed PU foaming AB material into a perfusion gun with a pressure sensor, and inject it through the injection port of the upper mold at a constant pressure to make the AB material uniformly fill the upper mold cavity and contact the surface of the lower re-coating layer.

[0084] S1063: Start the mold heating system, raise the temperature of the upper mold to the preset temperature and maintain a constant temperature, trigger the foaming reaction of the AB material, and maintain the preset gap between the upper and lower molds during the foaming process through the mold clamping force, so that the PU layer after foaming and the re-coating layer realize chemical bonding through intermolecular forces.

[0085] S107: After molding, cut the formed front wall sound insulation pad by using the cutting knife mold integrated on the blister foaming die.

[0086] S107 specifically includes the following steps: S1071: After molding and curing, detect the curing state of the material in the mold; S1072: Set the down pressure and cutting speed parameters of the cutting knife mold, take the positioning pin of the mold cavity as the reference, and start the cutting driving mechanism to drive the knife mold downward; S1073: After cutting, the mold is opened, and the cut composite structure is taken out, the edge waste is separated, and the formed front wall inner sound insulation pad is obtained.

[0087] The embodiment matches the cutting pressure according to the total thickness of the material, sets the cutting speed to reduce the stress damage of the material, calibrates the track based on the positioning pin, and ensures that the cutting position matches the design contour. The air bag driving and rotary mold opening provide sufficient operation space for taking out the part, peel off the waste material along the cutting trace, and ensure the integrity of the body contour.

[0088] S108: The front wall inner sound insulation pad is fixed on the front wall sheet metal by the elastic sheet buckle and the projection welding stud, and the EPP foot pad is installed on the co-driver side.

[0089] S108 specifically includes the following steps: S1081: In the direction of the re-coated layer facing the engine compartment, the front wall inner sound insulation pad is preliminarily aligned with the several projection welding studs on the front wall sheet metal assembly, so that the mounting holes punched out of the front wall inner sound insulation pad pass through the corresponding projection welding studs one by one, realizing positioning and suspension.

[0090] In some embodiments, in the assembly station, the front wall sheet metal assembly usually ends the painting process and is in a disassembled state or fixed on a fixture at a specific angle. A plurality of projection welding studs of standard height are pre-welded on the sheet metal, and the distribution positions of these studs correspond one by one to the positions of the round holes punched out on the front wall inner sound insulation pad. The operator aligns and fits the largest several main positioning holes on the front wall inner sound insulation pad with the most protruding several projection welding studs on the sheet metal, realizing guidance. After fitting, the front wall inner sound insulation pad is suspended on these studs under the action of gravity, and the remaining mounting holes are also basically aligned with the corresponding studs, and the front wall inner sound insulation pad is temporarily supported in the approximate installation position, but not fastened.

[0091] S1082: A pressing force is applied to the front wall inner sound insulation pad suspended on the projection welding studs towards the sheet metal surface, causing the elastic deformation of the metal elastic sheet buckle in the remaining mounting holes, until the locking structure of the buckle passes over the thread root of the projection welding stud and is tightly clamped after springback, completing the fixation between the body and the sheet metal.

[0092] In some embodiments, after the suspension is completed, the front wall inner sound insulation pad is finally compacted and locked on the surface of the sheet metal. The buckle of the front wall inner sound insulation pad is punched from spring steel and has a petal shape or an elastic claw hook with an inward turning, and its inner diameter is slightly smaller than the outer diameter of the projection welding stud. When a uniform pressure is applied to the front surface of the front wall inner sound insulation pad perpendicular to the sheet metal, the front wall inner sound insulation pad approaches the sheet metal. With the continuous pressure, the elastic claw hook is squeezed by the stud to cause elastic deformation outward, and the stud continues to penetrate into the inside of the buckle. The end is just clamped below the thread root or the back of the boss, serving as a locking. The elastic sheet buckle and the projection welding stud form a mechanical interlocking, tightly clamping the front wall inner sound insulation pad on the sheet metal, preventing it from moving in all directions.

[0093] S1083: In the area of the front wall on the side of the co-pilot, the foot mat block made of independent EPP material is molded into the corresponding position of the clamping groove on the sound insulation pad in the front wall by the bottom surface of the pre-set clamping structure. Pressure is applied to make it embedded and locked, and the assembly of the block is completed.

[0094] In some embodiments, the EPP foot mat block is a component independent of the production of the sound insulation pad in the front wall, which is molded by foaming polypropylene material through a mold, has a specific geometric shape and high impact energy absorption characteristics. After the main fixation of the sound insulation pad in the front wall and the sheet metal is completed, the operator takes the EPP block and aligns the buckle on the bottom surface with the clamping groove on the body. Pressure is applied to the block in the vertical direction. The EPP material has a certain elasticity, and the buckle structure is slightly compressed and deformed when inserted into the clamping groove. Once fully inserted, the buckle expands to its original shape, and the barb hooks the inner wall of the clamping groove, forming a firm connection. It ensures that the EPP block plays a role in buffering and absorbing energy as designed in a collision accident, protecting the lower leg of the occupant.

[0095] It should be understood that the size of the serial number of each step in the above embodiments does not mean the order of execution. The execution order of each process should be determined according to its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0096] It should be understood that when it is said that a certain element or layer is on, connected or coupled to another element or layer, it can be directly on, directly connected or coupled to the other element or layer, or there can be an intermediate element or layer. Conversely, when it is said that a certain element is directly on, directly connected or directly coupled to another element or layer, there is no intermediate element or layer. Similar numbers in all drawings indicate similar elements. As used herein, the term and / or includes any and all combinations of one or more of the related listed items.

[0097] Spatially relative terms such as under, below, lower, above, upper, and the like, can be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if a device is turned over, elements described as under or below other elements or features would then be oriented upward or above the other elements or features. Thus, the exemplary term below can encompass both an orientation of above and below. The device can be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

[0098] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present document. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms comprises and / or comprising, when used in this specification, include the meaning provided in the

[0099] The above description of disclosed embodiments provides examples, and is not intended to limit the scope, applicability or configuration of the application. Various modifications can be made to the disclosed embodiments, and other implementations can be used without departing from the spirit or scope of the application. Therefore, the above description is not intended to limit the scope of the application but is merely intended to provide an overview of the methods and systems described herein. Accordingly, the application is not limited to that precisely as shown and described and can be freely modified within the scope of the appended claims.

Claims

1. A method for preparing a sound insulation pad for the front bulkhead of an automobile, characterized in that the method... The method comprises the following steps: S101: Obtain the three-dimensional modeling data of the vehicle and the peripheral boundary conditions of the front wall assembly arrangement, and determine the thickness distribution range of the front wall inner sound insulation pad; S102: In the thickness distribution range, divide the front wall inner sound insulation pad into multiple regions, and predict the sound insulation amount of each region according to the sound source load distribution data; S103: Compare the predicted sound insulation amount of each region with the preset target sound insulation amount, and adjust the thickness distribution of the front wall inner sound insulation pad according to the comparison result; S104: According to the adjusted thickness distribution, the front wall inner sound insulation pad is composed of a PU foaming layer, a heavy coating layer and a sound insulation layer containing an EVA layer and a double-component cotton layer; S105: The heavy coating layer material corresponding to the heavy coating layer is heated and softened, and is placed in the lower mold of the plastic absorption foaming punching mold; S106: Inject the matched PU foaming AB material into the upper mold of the plastic absorption foaming punching mold, so that the PU foaming AB material foams and adheres on the heavy coating layer to form a shape; S107: After the mold pressing is completed, the cutting is performed through the cutting knife mold integrated on the plastic absorption foaming punching mold, so that the formed front wall inner sound insulation pad is obtained; S108: The front wall inner sound insulation pad is fixed on the front wall sheet metal through the spring buckle and the projection welding stud, and the EPP foot pad block is installed on the co-driver side.

2. The automobile front wall inner sound insulation pad preparation method according to claim 1, wherein S101 specifically comprises the following steps: The CATIA format three-dimensional modeling data corresponding to the target commercial vehicle front wall assembly is called, and the installation parameters of the butt joint parts on the front wall sheet metal are collected by using a point site mapping tool. The butt joint parts include wire harness mounting points, brake pedal mounting points, accelerator pedal mounting points and air conditioning hot water pipe mounting points; The collected installation parameters of each butt joint part are converted into the space occupation range in the three-dimensional modeling space, and the minimum gap threshold between the front wall inner sound insulation pad and each butt joint part is set; Combining the space profile of the three-dimensional modeling data and the minimum gap threshold, multiple regions of the front wall inner sound insulation pad are divided and the initial thickness of each region is distributed, and the upper and lower limits of the thickness distribution range of the front wall inner sound insulation pad are determined by calculating the thickness average value of each region.

3. The automobile front wall inner sound insulation pad preparation method according to claim 1, wherein S102 specifically comprises the following steps: A light commercial vehicle front wall sound source test bench is built, four running conditions of idle speed, uniform speed, 5th gear full throttle and 6th gear full throttle are selected, and the sound pressure level data of the corresponding regions of the front wall assembly under each condition is collected. The sound pressure level data is converted into the sound source load values at each position; The sound source load values collected under each condition are matched to the corresponding regions one by one according to the space projection range of the front wall inner sound insulation pad regions divided in S101, and the sound source load distribution set of each region is obtained; Based on the statistical energy simulation analysis method, the acoustic subsystem model corresponding to each region of the front wall inner sound insulation pad is established, the material parameters of each region are substituted, the sound insulation amount of each region is calculated by combining the region material layer thickness average value formula.

4. The automobile front wall inner sound insulation pad preparation method according to claim 1, wherein S103 specifically comprises the following steps: ​ ​ ​ The front assembly target sound insulation amount obtained based on the decomposition of the whole vehicle NVH performance is retrieved, and the corresponding region target sound insulation amount is matched region by region according to the division of S102, and a judgment threshold of sound insulation amount comparison is set; The average thickness of each region after the initial thickness distribution of the region divided in S101 is analyzed, and the current thickness of each region is compared with the average thickness, and the region with a thickness greater than or equal to the average thickness is defined as a thick region, and the region with a thickness less than the average thickness is defined as a thin region; The predicted sound insulation amount of each region is compared with the corresponding region target sound insulation amount and the judgment threshold respectively; if the predicted sound insulation amount is less than (target sound insulation amount-judgment threshold), the thickness of the corresponding thin region is increased or the area proportion thereof is reduced; if the predicted sound insulation amount is greater than (target sound insulation amount+judgment threshold), the thickness of the corresponding thick region is reduced or the area proportion thereof is reduced.

5. The automobile front wall inner sound insulation pad preparation method according to claim 1, wherein S104 specifically comprises the following steps: S104 specifically comprises the following steps: The total thickness of each region after the adjustment of S103 is extracted, and the total thickness of each region is decomposed into the thickness of the PU foaming layer, the thickness of the heavy coating layer, the thickness of the EVA layer and the thickness of the double-component cotton layer, thereby forming a layered thickness distribution table of each region; According to the assembly direction and the acoustic propagation path of the front wall inner sound insulation pad, the layering order of the multi-layer composite material is determined as: heavy coating layer, PU foaming layer, EVA layer, double-component cotton layer, wherein the double-component cotton layer faces the driver's cabin side, and the heavy coating layer faces the front wall metal side; The specification parameters of each layer of material are fixed, and the interlayer bonding mode is determined.

6. The automobile front wall inner sound insulation pad preparation method according to claim 1, wherein S105 specifically comprises the following steps: The lower die cavity of the heavy coating layer material is cut to adapt to the lower die cavity of the plastic absorption foaming punching die, and the lower die of the punching die is cleaned and defect-preprocessed; The cut heavy coating layer material is placed in an oven to be heated to a softened state; The opening and closing state of the plastic absorption foaming punching die is adjusted, the heavy coating layer material in the softened state is positioned and placed in the lower die after the lower die cavity of the punching die is sprayed with a demolding agent.

7. The automobile front wall inner sound insulation pad preparation method according to claim 1, wherein S106 specifically comprises the following steps: The mass ratio of A material and B material is calculated according to the PU foaming density specification 60 kg / m³, the corresponding mass of A material and B material is weighed by using an electronic scale, and the A material and B material are mixed by using a double-shaft mixer; The mixed PU foaming AB material is loaded into a perfusion gun with a pressure sensor, and is injected into the upper die cavity through the injection port of the upper die at a constant pressure, so that the AB material is uniformly filled in the upper die cavity and contacts the surface of the lower heavy coating layer; The upper die temperature is increased to a preset temperature and kept constant by starting the die heating system, the foaming reaction of the AB material is triggered, and the upper and lower dies are kept at a preset gap by the die clamping force during the foaming process, so that the PU layer after foaming and the heavy coating layer are chemically bonded by intermolecular force.

8. The automobile front wall inner sound insulation pad preparation method according to claim 1, wherein S107 specifically comprises the following steps: After the mold pressing and curing are completed, the curing state of the material in the mold is detected; The down pressure and cutting speed parameters of the punching cutter die are set, the positioning pin of the die cavity of the mold is taken as a reference, and the punching driving mechanism is started to drive the cutter die to move downward. ​ ​ ​ After the cutting is completed, the mold is opened, the cut composite structure is taken out, the edge waste is separated, and the formed front wall sound insulation pad is obtained.

9. The automobile front wall sound insulation pad preparation method according to claim 1, characterized in that, S108 specifically comprises the following steps: In the direction of the re-coating layer facing the engine compartment, the front wall sound insulation pad is preliminarily aligned with the several projection welding studs on the front wall sheet metal assembly, the mounting holes punched out of the front wall sound insulation pad are sequentially threaded through the corresponding projection welding studs, positioning and suspension are realized; A pressing force is applied to the front wall sound insulation pad suspended on the projection welding studs towards the sheet metal surface, the metal spring buckles in the remaining mounting holes are elastically deformed until the locking structure of the buckle passes the thread root of the projection welding stud and is tightly clamped after springback, the fixing between the body and the sheet metal is completed; In the front wall area of the co-pilot, the foot pad block made of independent EPP material is molded into the clamping groove on the corresponding position of the front wall sound insulation pad in the direction of the bottom surface of the preset clamping structure, pressure is applied to embed and lock it, and the assembly of the pad block is completed.

10. A front panel having a soundproofing pad, characterized by Comprise: The front wall sound insulation pad (6) prepared based on the preparation method in any one of claims 1 to 9; The front wall sound insulation pad (6) is fixed on the front wall sheet metal (4) through the projection welding stud (5) and the buckle (7); The EPP foot pad block (8) is installed on the co-pilot side of the front wall sheet metal (4); The front wall sound insulation pad (6) is provided with a sound insulation layer (1), a re-coating layer (2) and a PU foaming layer (3).

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